Pump system for high pressure application

ABSTRACT

A pump system for high pressure, high volume applications is presented. The pump system includes a turbo-shaft engine having a drive shaft and a high pressure, high RPM centrifugal pump coupled to the drive shaft. In certain embodiments the pump system further includes a second low pressure, high RPM centrifugal pump coupled to the drive shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims the benefit of andpriority to, U.S. patent application Ser. No. 14/442,039, filed on May11, 2015, which is a National Stage Entry of International ApplicationNo. PCT/US2013/069463, filed on Nov. 11, 2013, which claims the benefitof and priority to U.S. Provisional Patent Application Ser. No.61/725,880, filed on Nov. 13, 2012. The entire contents of each of theabove-identified applications are hereby incorporated by reference.

FIELD

The present invention relates generally to pump systems for highpressure pumping applications, and more particularly to pump systems forhydraulic fracturing.

BACKGROUND

Traditionally, high pressure, high volume pumping applications usediesel reciprocating engines to drive a reciprocating pump. In the fieldof hydraulic fracturing, or fracking, conventional diesel reciprocatingengines have been replaced with turbine engines because the lower weightand easier deployment of turbine engines allow for improved speed ofdelivery, deployment, and uptime. As a result, pump system designs forhydraulic fracturing utilize a high speed take-off from a turbine engine(e.g., approaching 15000 RPM), through a gear reduction box, and into areciprocating pump. The primary inefficiencies in such systems come fromthe gearbox (e.g., about 8% loss for an 8:1 gear reduction ratio) andthe reciprocating pump (e.g., about 6% loss). As a result, the totalloss in such systems from an output shaft of the engine to the totalhydraulic horsepower is about 14%. In addition, while turbine enginesprovide an improvement over conventional diesel engines, the entiresystem, including the turbine engine, gearbox, and reciprocating pumpstill requires a relatively large footprint on a truck or trailer bed inmobile pumping applications.

Therefore, there is a need for a high efficiency, small footprint pumpsystem for high pressure pumping applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will become more apparent from the detaileddescription set forth below when taken in conjunction with the drawings,in which like elements bear like reference numerals.

FIG. 1 illustrates a first pump system according to Applicant'sinvention;

FIGS. 2A-2C illustrate the front, cut-a-way, and back views,respectively, of the centrifugal pump of the pump system illustrated inFIG. 1;

FIGS. 3A and 3B illustrate top and side views, respectively, of atrailer bed including multiple pump systems, in accordance withApplicant's invention;

FIGS. 4A and 4B illustrate top and side views, respectively, of anothertrailer bed including multiple pump systems, in accordance withApplicant's invention;

FIG. 5 illustrates a graph of example pump output pressures at differentrotational speeds using the disclosed invention; and

FIG. 6 illustrates a second pump system according to Applicant'sinvention.

SUMMARY

In one implementation, a pump system for high pressure, high volumeapplications is presented. The pump system includes a turbo-shaft enginehaving a drive shaft and a high pressure, high RPM centrifugal pumpcoupled to the drive shaft. In certain embodiments the pump systemfurther includes a second low pressure, high RPM centrifugal pumpcoupled to the drive shaft.

In another implementation, a high pressure pump system is presented. Thesystem includes multiple pump systems each having a turbo-shaft enginehaving a drive shaft, and a first centrifugal pump coupled to the driveshaft. The multiple pump systems are then mounted to a platform ineither a horizontal, vertical, or angled vertical position. In certainembodiments, the system includes four or more pump systems.

In another implementation, a method of performing high pressure, highvolume pumping applications is presented. The method includes providinga system having multiple pump systems each having a turbo-shaft enginehaving a drive shaft, and a first centrifugal pump coupled to the driveshaft. The multiple pump systems are mounted to a platform in either ahorizontal, vertical, or angled vertical position. The method furtherincludes pumping a fluid at an output pressure greater than 5000 psi.

DETAILED DESCRIPTION

This invention is described in preferred embodiments in the followingdescription with reference to the Figures, in which like numbersrepresent the same or similar elements. Reference throughout thisspecification to “one embodiment,” “an embodiment,” or similar languagemeans that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the present invention. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” and similar language throughout thisspecification may, but do not necessarily, all refer to the sameembodiment.

The described features, structures, or characteristics of the inventionmay be combined in any suitable manner in one or more embodiments. Inthe following description, numerous specific details are recited toprovide a thorough understanding of embodiments of the invention. Oneskilled in the relevant art will recognize, however, that the inventionmay be practiced without one or more of the specific details, or withother methods, components, materials, and so forth. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the invention.

Applicant's invention includes a pump system for high pressureapplications. Such applications, including but not limited to hydraulicfracturing applications, can require pressures greater than about 5000pounds per square inch (psi) and volumes greater than about 55 barrelsper minute in aggregate. Turning now to FIG. 1, an exemplaryillustration of the pump system 10 of Applicant's invention is presentedwith a portion of the pump system housing cut-away for illustrativepurposes only. As shown in FIG. 1, the pump system 10 includes aturbo-shaft engine 12 and a centrifugal pump 14. As will be appreciated,turbo-shaft engines are a type of high RPM (rotations per minute) gasturbine engines which are optimized to produce shaft power and arecommonly used in military vehicular applications, such as inhelicopters, ships, tanks, and hovercraft. As used herein, “high RPM”refers to at or greater than 13,000 RPM. In certain embodiments, theturbo-shaft engine 12 runs at greater than 15,000 RPM. In certainembodiments, the turbo-shaft engine 12 runs at greater than 20,000 RPM.In certain embodiments, the turbo-shaft engine 12 runs at greater than30,000 RPM. As illustrated here, the turbo-shaft engine 12 includes adrive shaft 16, an intake section 18, a compressor section 20, acombustion chamber 22, and an exhaust portion 24.

The centrifugal pump 14 is a high pressure high RPM pump that uses asplit impeller design comprising a main impeller portion 34 and asecondary impeller portion 33. As used herein, “high pressure” refers togreater than 5000 psi. In certain embodiments, centrifugal pump 14 runsat greater than 10,000 psi. In certain embodiments, centrifugal pump 14runs at greater than 15,000 psi. In certain embodiments, centrifugalpump 14 runs at greater than 20,000 psi. As is shown in FIG. 1, thecentrifugal pump 14 includes a housing comprising the body 26 having aninput chamber 28 and an output chamber 32, back plate 27, and aremovable cap 29. The pump body 26 and the back plate 27 are heldtogether with multiple mechanical fasters and together form a volute 30,in which the main impeller portion 34 is positioned. The impellerportion 33 is separately housed under the removable cap 29 to allow forserviceability, as will be discussed below.

Additional illustrations of centrifugal pump 14 are shown in FIGS.2A-2C. As can be seen in FIG. 2C specifically, the back plate 27includes inlet 37 to allow wash water to be injected into pump 14 asnecessary to keep debris from accumulating on the back side of impellerportions 33 and 34.

As shown in FIG. 1, the drive shaft 16 can be mechanically coupled tothe impeller (portions 34 and 33) via a rotor shaft 17 and coupler 64(shown in FIG. 6) to drive the impeller for pumping fluid from the inputchamber 28 through the output chamber 32. In some embodiments, the rotorshaft 17 can include multiple heat-fitted pieces that, once coupledtogether, are static with respect to one another. One or more bearings,such as bearings 31 and 35 (FIG. 2C), can be positioned around the rotorshaft 17 to prevent oscillation and vibrations during operation of thepump system 10 and reduce wear on components of the centrifugal pump 14.In some embodiments, one or more engine bearings (not shown) positionedaround the drive shaft 16 can replace one or more of the bearingspositioned around the rotor shaft 17.

Due to the rotor shaft 17 being the only moving part of the centrifugalpump 14, as well as the lack of valves and internal catch points, thecentrifugal pump 14 is generally very durable and requires littlemaintenance with respect to the industry standard for equipment used infracking operations. For example, maintenance required for thecentrifugal pump 14 can include replating the impeller vanes 36 orinternal surfaces of the volute 30, or replacing dynamic or static sealsaround the rotor shaft. This is substantially less maintenance work thanwhat is necessary for triplex or quadruplex reciprocating pumps, whichinclude multiple moving valves and pistons in comparison to the singlemoving rotor shaft of the centrifugal pump 14. In addition, due to thelack of valves and internal catch points, the centrifugal pump 14 iscapable of pumping fluids including inconsistent mixtures of solids andliquids, such as wet sand mixtures or bentonite clay for hydraulicfracturing applications.

The split impeller design of centrifugal pump 14 further adds to itsdurability and ease of maintenance. As will be appreciated of theimpeller, secondary impeller portion 33 is likely to experience higherwear than main portion 34. Accordingly, the split impeller design anduse of removable cap 29 to cover secondary impeller portion 33 allowsfor easy maintenance and replacement of this portion as needed.

In certain embodiments, the interior of centrifugal pump 14, the mainimpeller portion 34, the secondary impeller portion 33, and the cap 29are coated or sleeved with a low friction plastic to help reducefriction and overall wear of the system.

Referring back to FIG. 1, the impeller is rotated directly by the outputshaft 16 to achieve a desired output pressure of fluid through theoutput chamber 32 (i.e., without requiring an additional gearboxassembly between the turbo-shaft engine 12 and the centrifugal pump 14).In one embodiment, for hydraulic fracturing applications, theturbo-shaft engine 12 drives the shaft 16 at a rotational speed betweenabout 13,000 rotations per minute (RPM) and about 18,000 RPM. In certainembodiments, the main impeller portion 34 has a diameter of about 26inches at its widest portion and is rotated at the same speed as theshaft 16 to achieve output pressures between about 15,000 pounds persquare inch (psi) and about 20,000 psi for fluids with a specificgravity between about 0.59 and about 1.92 (e.g., relative to water witha specific gravity of 1.0). By “about” Applicant means±10%.Additionally, with reference to hydraulic fracturing applications, thepump system 10 includes a 23-inch diameter impeller 34, a 26-inchdiameter impeller, a 30-inch diameter impeller, or another suitable sizeimpeller. FIG. 5 illustrates example output pressures of water, wetsand, and bentonite clay pumped at different rotational speeds by pumpsystem 10 including a 26-inch diameter impeller and a 30-inch diameterimpeller.

Turning now to FIG. 6, an alternate embodiment of Applicant's pumpsystem is illustrated. As can be seen, the pump system 50 comprises asecond centrifugal pump 52 connected to the first centrifugal pump 14and the turbo-shaft engine 12. This second centrifugal pump 52 is a lowpressure high RPM centrifugal pump of the same split impeller design aspump 14. In the present context, “low pressure” refers to pressuresbelow 5000 psi. In certain embodiments, the second centrifugal pump hasthe same diameter as the first centrifugal pump. In other embodiments,the second centrifugal pump has a different diameter as the firstcentrifugal pump. In certain such embodiments, the diameter of thesecond centrifugal pump is smaller than the diameter of the firstcentrifugal pump. In other such embodiments, the diameter of the secondcentrifugal pump is larger than the diameter of the first centrifugalpump.

As is shown in FIG. 6, the second centrifugal pump 52 is connected tothe first centrifugal pump 14 via coupler 61 and second rotor shaft 60which drives the second centrifugal pump 52. This second centrifugalpump 52 allows the turbo-shaft engine 12 to run nearer to its optimalRPM range without requiring a transmission. As will be appreciated,transmissions generally are designed to have a high attenuation anddissipate energy. Accordingly, Applicant's pump system 50 is moreefficient than those of the prior art.

Additionally, the use of a second centrifugal pump increases the rangeof fracking operations that Applicant's pump can be used for. Typicalfracking operations may require pressures of anywhere from 5000 psi to15,000 psi. Most individual centrifugal pumps cannot be safely orefficiently run across that great of a pressure range. By having twocentrifugal pumps, Applicant's pump system 50 can safely and efficientlyoperate at a broad range of pressures.

As described above, in certain embodiments the pump system 10 and/or 50achieves desired impeller speeds and output pressures without requiringa gearbox assembly. As will be appreciated, the elimination of a gearboxassembly greatly reduces the footprint and weight of the pump systems 10and 50 in comparison to traditional pump systems. This is anadvantageous feature for mobile pumping applications, where one or morepump systems are installed on a truck or trailer bed, since smallerindividual footprints can allow for additional pumps systems to beinstalled on the same trailer bed. The elimination of a gearbox, and theability for the turbo-shaft engine 12 to be mounted horizontally orvertically, also allows for the pump system 10 to be mounted to a truckin a traditional horizontal orientation or a vertical orientation, asshown in FIGS. 3A and 3B. One will appreciate that while FIGS. 3A and 3Bare illustrated with pump system 10, the present discussion is equallyapplicable to pump system 50. By way of illustration and not limitation,FIG. 6 further illustrates pump system 50 mounted horizontally on aplatform 51 using braces 53 and 55 to stabilize turbo-shaft engine 12.

FIGS. 3A and 3B illustrate a trailer bed 38 for a hydraulic fracturingapplication including multiple pump systems 10 mounted in the verticalorientation and connected in parallel by pipe connections 40. In someembodiments, the number of pump systems 10 capable of being mounted onthe single trailer bed 38 is between four and seven (as shown in FIGS.3A-3B and 4A-4B). In other embodiments, the number of pump systems 10capable of being mounted on a single trailer bed 38 is greater thanseven. The pump systems 10 can receive fracking fluid (i.e., from asingle inlet 42 to each of the input chambers 28) at a low pressure fromone or more slurry blenders (not shown) through the pipe connections 40.The pump systems 10 can then output pressurized fracking fluid (i.e.,from each the output chambers 32 to a single outlet 44) through the pipeconnections 40 toward a well (not shown).

As shown in FIGS. 3A and 3B, when mounted in the vertical orientation,each pump housing (i.e., a side of the pump housing opposite theturbo-shaft engine 12) can be positioned flat against the trailer bed 38or against skids on the trailer bed 38. As a result, the output chamber32 of the pumps 14 can be closer to the ground, which reduces the lengthof pipe connections 40 necessary for hydraulic fracturing or otherground pump applications. This reduces the overall equipment costssince, in hydraulic fracturing, the pipe connections 40 can besubstantially large, including diameters between about 3 inches andabout 5 inches. In addition, by positioning the pump systems 10 in thevertical orientation, the exhaust nozzles 24 point straight up so thatexhaust is directed up and away from the pump systems 10. In someembodiments, a hatch (not shown) can be positioned over each exhaustnozzle 24 to prevent rain inflow into the turbo-shaft engines 12.

In some embodiments, arranging the pump system 10 in the verticalorientation reduces the stress on the dynamic seal between the rotorshaft and the pump housing, which is often the most maintenance pronecomponent of the centrifugal pump 14. To achieve proper operation of thecentrifugal pump 14 without the dynamic seal, the area between theturbo-shaft engine 12 and the pump housing can be enclosed and aninternal cavity created by the enclosure (i.e., around the shaft 16) canbe filled with air pressurized to match the pressure of fluid enteringthe input chamber 28. For example, in hydraulic fracturing applications,the air can be pressurized to match the pressure of fracking fluidentering the input chamber 28 (i.e., the input pressure) from the slurryblenders. In those embodiments which include a dynamic seal, theinternal cavity surrounding the shaft 16 is pressurized at or above theinput pressure and a weep hole is provided so that, when the dynamicseal around the shaft 16 is violated due to wear and tear, the leakedpumping fluid can be collected. In hydraulic fracturing applications, orother pump applications, this weeped material is fed back into theslurry blenders to prevent unnecessary waste.

FIGS. 4A and 4B illustrate another trailer bed 38 for a hydraulicfracturing application including six pump systems 10 mounted in anangled vertical orientation and connected in parallel by pipeconnections 40 between a single inlet 42 and a single outlet 44. As withFIGS. 3A and 3B, while FIGS. 4A and 4B illustrate mounting positions forpump system 10, the present discussion is equally applicable to pumpsystem 50. The angled vertical orientation shown in FIGS. 4A and 4Ballows the turbo-shaft engines 12 to be pitched backwards (e.g., about20 degrees from vertical, or another suitable angle). As a result, thepump systems 10 still create a smaller footprint compared to traditionalpump systems and conventional oil sumps 48 of the engines 12, as shownin FIG. 4B, do not need to be changed or redesigned (for example, toaccommodate the full vertical orientation of FIGS. 3A and 3B).

As described above, in certain embodiments the pump systems 10 and 50 ofApplicant's invention has a reduced footprint in comparison totraditional pump systems. This is advantageous in many situations. Forexample, because of the large size of traditional pump systems,typically only one or two pump systems can fit on a single trailer bed.Fracking applications can commonly require 20 trucks or more using pumpsystems with reciprocating engines or 10 trucks or more usingtraditional turbine-driven pump systems to obtain a necessary pressureand volume, resulting in an average of two to four days for set up.However, as shown in FIGS. 3A and 3B, because of the reduced footprintof Applicant's invention, as many as seven pump systems 10 (or pumpsystems 50 or a combination thereof) may fit on the same sized singletrailer bed (trailer bed 38). Because fewer trucks are used, the truckset up time is reduced to about four hours.

In addition to the reduced number of trucks and set up time, the pumpsystems 10 of Applicant's invention also allows for reduced teardowntime in comparison to using traditional pump systems. Thus, the smallerfootprint of the pump systems 10 reduces the capital equipment costs ofthe trucks and the operational costs of transportation and maintenance.The smaller number of trucks and equipment also reduces the impact onthe environment at the fracturing site.

The pump system 10 and pump system 50 of Applicant's invention alsoprovides improvements over traditional pump systems in terms ofefficiency. More specifically, the combination of the turbo-shaft engine12 and the centrifugal pump 14 is more efficient for high pressure(e.g., greater than about 5000 psi), high volume (e.g., greater thanabout 65 barrels per minute per pump) applications than otherconventional pump system arrangements. For example, turbine-drivenreciprocating pump systems require a gearbox reduction that reducesefficiency by about 6% to 8%, while the reciprocating pump reducesefficiency by another 6%, resulting in approximately 86% efficiency fromoutput shaft to total hydraulic horsepower. In another example, a pumpsystem including a conventional diesel reciprocating engine driving acentrifugal pump requires a gearbox reduction that reduces efficiency byabout 10% to 14%, in addition to the efficiency reduction through thecentrifugal pump. Due to the elimination of a gearbox assembly, theturbine-driven centrifugal pump system 10 (or system 50) of Applicant'sinvention is approximately 94% efficient from output shaft to hydraulichorsepower. The higher efficiency of the turbine-driven centrifugal pumpsystem 10 of Applicant's invention reduces fuel consumption necessary toachieve the same output as traditional assemblies, thus decreasingoperational costs. In addition, due to the high efficiency output ofApplicant's invention, in certain embodiments fuel additives requiredfor traditional systems are minimized or eliminated, further decreasingoperational costs.

Referring back to FIGS. 3A and 3B, in certain embodiments the trailerbed 38 also includes an auxiliary power unit (APU) 46 and one or moreengine or pump system controllers (not shown). In some embodiments, thepump system controllers controls the turbo-shaft engine's compressorshaft speed (N1 speed), the turbine shaft or output shaft speed (N2speed), the pressure at the output chamber 32, and/or the flow rate offluid through the output chamber 32. The compressor shaft and theturbine/output shaft 16 are concentric shafts that are pneumaticallycoupled to each other. As will be clear to one of ordinary skill in theart, the compressor shaft creates the air pressure through theturbine-shaft engine 12 that drives the turbine/output shaft 16. Thepump system controllers control the effects of engine unloading duringoperation of the pump systems, for example due to pressure spikes orblockages at the output chamber 32, which can cause an increase in theN2 speed. In addition, in some embodiments, mechanically blocking theoutput chamber 32 (e.g., via outlet valves, not shown) is necessary tounload the engine 12 and reduce the power necessary for engine startup.In other embodiments, this is not necessary due to bleed valves (notshown) positioned at the compressor section 20.

While the preferred embodiments of the present invention have beenillustrated in detail, it should be apparent that modifications andadaptations to those embodiments may occur to one skilled in the artwithout departing from the scope of the present invention.

What is claimed is:
 1. A pump system for high pressure applications,comprising: a first centrifugal pump including a coupling configured forattachment to a predetermined configuration of drive shaft of an engine,the first centrifugal pump further comprising: a split impeller having afirst portion and a second portion; a housing formed to include avolute, wherein the first portion of the split impeller is situated inthe volute; and a removable cap, wherein the second portion of the splitimpeller is covered by the removable cap.
 2. The pump system of claim 1,wherein the first centrifugal pump is a high pressure centrifugal pump.3. The pump system of claim 1, wherein the first centrifugal pump is ahigh rotations-per-minute (“RPM”) centrifugal pump.
 4. The pump systemof claim 1, wherein the housing further comprises a back plate, whereinthe back plate includes an inlet to receive injection of wash water. 5.The pump system of claim 1, further comprising a second centrifugal pumpcoupled to the drive shaft.
 6. The pump system of claim 5, wherein thefirst centrifugal pump is a high pressure centrifugal pump and thesecond centrifugal pump is a low pressure centrifugal pump.
 7. The pumpsystem of claim 5, wherein the first centrifugal pump and the secondcentrifugal pump are high rotations-per-minute (RPM) centrifugal pumps.8. The pump system of claim 5, wherein: the first centrifugal pump has afirst diameter, the second centrifugal pump has a second diameter, andthe first diameter and the second diameter differ.
 9. The pump system ofclaim 1, further comprising an engine coupled to the first centrifugalpump.
 10. The pump system of claim 9, wherein the engine and the firstcentrifugal pump are coupled free of any gearbox.
 11. A high pressurepumping system comprising: a plurality of pump systems, each comprising:an engine; and a first centrifugal pump coupled to the engine, the pumphaving an axis of rotation; and a platform upon which the plurality ofpump systems are mounted, wherein each of said pumps is mounted on theplatform in one of the following configurations with respect to the axisof rotation of said pump: (1) vertically, (2) an angled verticalorientation.
 12. The system of claim 11, wherein the plurality of pumpsystems includes at least four pump systems.
 13. The system of claim 11,wherein: each of the plurality of pump systems further comprises asecond centrifugal pump coupled to the drive shaft; the firstcentrifugal pump is a high pressure centrifugal pump; and the secondcentrifugal pump is a low pressure centrifugal pump.
 14. The system ofclaim 11, wherein: each of the plurality of pump systems furthercomprises a second centrifugal pump coupled to the drive shaft; and thefirst centrifugal pump and the second centrifugal pump are highrotations-per-minute (RPM) centrifugal pumps.
 15. The system of claim11, wherein each of the pump systems is free of any gearbox between theengine and the first centrifugal pump.